1. Field of the Invention:
This invention relates to master track links, and more particularly to two-piece master track links for connecting an endless track of the type used in chains, track-type tracks and other articulated devices of a similar nature, especially in an endless track of a small sized bulldozer.
2. Description of the Prior Art:
In a track-type vehicle such as a bulldozer, an endless track comprises a plurality of track shoes carried by links which are pivotally connected by means of hinge pins and bushings.
It is conventional to provide a master pin or a master link in each continuous chain of links which may be retained securely in place while still permitting separation of the link chain for disassembly of the endless track from the vehicle. Master link connections normally comprises two link parts, each being adapted to receive a pin and having a mating surface to couple and interlock with that of the other link part. The respective mating surfaces of the link parts define a juncture of the master track link and each has an interlocking contact surface, these surfaces coacting to resist tensile force ad thrust force exerted on the link at the pin connections of each link part. Suitable means such as screws maintain the link parts in their mating interlocked relation while they are disposed within an endless track.
Pertinent prior art two-piece master track links disclosed in U. S. Pat. Nos. 3,427,079 and 3,822,923 have proven functionally effective. However, as to U. S. Pat. No. 3,427,079, it have been found difficult and costly to manufacture. Close tolerances are required to assure optimum coupling of the interlocking surfaces and alignment of the shoe bolts which respectively secure the track shoes associated link parts. Although the master pin requires a relative loose tolerances as compared with that of the regular pin in order to facilitate the connection and disconnection of the endless track, it is still required to use a hydraulically actuated tool or a manually actuated hammer for assemblying and disassemblying the endless track at the field of work, thereby rendering the assembly and disassembly of the endless track troublesome and difficult. Further, if the tolerances of the master pin is loosened too much, the master pin tends to be drawn out of the mating portion of the endless track, thereby resulting in damage in the endless track.
In addition, without a tight fit to minimize flexing between the link parts, concentrated stress loads and malfunction of hinge joints can occur with consequent progressive deterioration of the entire track chain. Contour grinding is an effective way of attaining the required precision machining of the extremely hard link members but such grinding is time consuming, costly and involved because the complex and expensive grinding wheel must be frequently refinished to maintain the desired tolerances.
Whereupon, U. S. Pat. No. 3,822,923 has been made to avoid the above described disadvantages. However, such U. S. Patent merely aims to minimize the above described manufacturing problems, and therefore it is still disadvantageous in that the mating surfaces of the two link parts lack in toughtfull consideration of withstanding thrust force exerted thereon at the pin connections of each link part. Namely, each of the mating surfaces of the subject master track link of U. S. Pat. No. 3,822,923 is provided with semicylindrical notches which register with corresponding complementing notches in the associated link part and receive close fitting cylindrical lock and shear keys. Such shear keys are further provided with diametral bores which receive shoe bolts used to secure the two link parts to each other together with the track shoe so as to prevent the shear keys from disengagement thereof. As a result, shearing strength of each shear key is remarkably reduced.
This invention contemplates to avoid all the above described disadvantages of the prior art two-piece master track link.